1. Field of the Invention
The present invention relates to methods for processing seismic data and more particularly to a method that provides a set of source and receiver statics corrections suitable for improving depth image.
2. Related Prior Art
Tomography has been used to modify velocity models. Time domain statics solutions are known to improve stacking in the time domain. However, prior art has not thought about solving the problem at the reflection point, where the solution is rigorously correct. The following patents are examples of prior art attempts at addressing this problem.
U.S. Pat. No. 4,592,032 titled "Methods of Processing Geophysical Data and Displays of Geophysical Data", issued to Gary M. Ruckgaber, relates to a seismic signal processing method in which seismic signals are processed to determine relative location error. The relative location errors are corrected and the corrected seismic signals are processed to give information on subsurface structure.
U.S. Pat. No. 4,839,869 titled "Methods for Processing Converted Wave Seismic Data" issued to Chris T. Corcoran, relates to methods for processing converted wave seismic data. This includes fractional point gathering of the data in a manner consistent with a selected velocity model, dynamic correction of the data using parameters measured from the data to account for the asymmetric travel path of the converted wave rays and stacking the dynamically corrected data. Methods are also provided for updating the velocity model.
U.S. Pat. No. 4,894,809 titled "Method for Bin, Moveout Correction and Stack of Offset Vertical Seismic Profile Data in Media with Dip" issued to George P. Moeckel, relates to processing vertical seismic profile data. Seismic energy is generated at a multiplicity of source offsets from a borehole and offset VSP data is collected by an acoustic detector at a multiplicity of geophone depths for each source offset. The recorded data is sorted into Zero Source-Receiver (ZSR), common reflection point bins. Data from each offset VSP, ZSR common reflection point gather are dynamically moveout corrected with data adaptive parameters including reduced direct arrival times, dip, borehole deviation and stacking velocities. The moveout corrected VSP data are then stacked.
U.S. Pat. No. 4,907,205 titled "Method for Attenuating Multiple Reflection Events in Seismic Data", issued to Dennis A. Yanchak, relates to a method for enhancing seismic data and, more particularly, for attenuating multiple reflection events in seismic data. Seismic data are sorted into common endpoint gathers, and selected multiple reflection events are corrected for time delays associated with the reflection of the seismic entry from common reflection interfaces and aligned. The aligned multiple reflection events are attenuated and the resulting enhanced seismic data can then be inverse time delay corrected for subsequent processing, including repetitions of the aligning and attenuation steps to suppress additional multiple reflection events in the seismic data.
U.S. Pat. No. 4,935,904 titled "Method for Suppressing Coherent Noise in Seismic Data", issued to Ronald E. Chambers, et al., relates to a method for removing boundary-generated artifacts in synthetic and actual seismic data. After seismic data processing, undesirable boundary-generated artifacts appear in the final seismic section. To remove this unwanted noise from section, zeros are added to the lower boundary of the seismic section. This essentially pushes the sources of the noise downward in time in the section. After padding with zeros, the seismic data is collapsed to the point sources of origin using the Stolt migration/diffraction algorithm. Once the data are collapsed, the size of the seismic section is reduced to its original size. Following the resizing of the section, the inverse of the earlier applied Stolt algorithm is applied to return the seismic data to its original form, minus the boundary-generated artifacts.
U.S. Pat. No. 4,980,866 titled "Common Offset Depth Migration with Residual Moveout Correction", issued to Shein S. Wang et al. relates to a method for applying residual moveout correction to common offset depth migrated data. Common offset depth migration is applied using the best available velocity/depth model. Post migrated parts, which are depth migrated common midpoint gathers, are saved. The post migrated parts are treated as if they were in time not depth. Normal moveout based on a constant velocity is removed. Velocity functions (time-velocity pairs) are derived for the post migrated parts with normal moveout removed using a standard velocity analysis program. Normal moveout based on these velocity functions is applied. The events on the post migrated parts are now imaged to the same depth. The corrected post migrated parts are then stacked and displayed.
U.S. Pat. No. 5,050,131 titled "Quantitative Method for Evaluating Velocity Model Quality", issued to Shein S. Wang et al., relates to a method for quantitatively determining an accurate subsurface velocity prior to data migration. This method includes steps whereby the accuracy of the velocity can be defined by measuring the deviation in depth as a function of offset in the common reflection point (CRP) gather. A point on reflector is selected and the CRP gather is formed. If the image is not flat, the velocity is adjusted until it is flat. The velocity is decreased and the far offset end of the image will be imaged to shallower depth than the near offset end. The velocity is increased and the image will tilt down at the far offset end. An error is defined which is the theoretical accuracy limit for the determination of velocity using the CRP method. A factor is defined that indicates the reliability of the image for a reflector.